Television scanning disk



Patented Sept. 19, 1939 TEmvIsroN scANNnvG msx Kurt Heinz Graefe, Berlin, Germany, assigner tolladioaktiengsellschait D. S. Loewe, BerfI lin-Steglitz, Germany, a company of Germany Application March 7, 1938, Serial No. 194,359 Y In Germany March 8, 1937 l 3 Claims.

The present invention relates to television scanning disks and more particularly to disks upon which,in order to avoid the so-called keystone distortion, the scanning light bundle falls at an inclined angle.

If the scanning holes of thel disk are punched as usual in the form of circles, squares or other regular polygons the oblique passage of the light causes some disadvantages which will be explained later on.

It is an object of the invention to avoid these 4disadvantages by forming the holes in a special way.

Further objects of the invention may be best understood by reference to the following description taken in connection with the accompanying drawing in which Fig. 1 is a side view of a scanning disk as used hitherto and of the oblique light ray whilst Figs. 2 to 4 show different embodiments of the invention, i Figs. 2a, 3a and 4a in cross-section.

Figs. 2b and 2c, 3b and 4b in front view.

In Fig. 1 IIv is the scanning disk provided with holes I2 throughwhich the bundle of iight I5, after having traversed lm I4 and `lens I3, passes at an angle a. Consequently the useful crosssection of the hole for the bundle is reduced by the factor cos a, if the thickness of the disk is zero, and still more if the thickness is of the same order of magnitude as the diameter of the hole.

A further disadvantage when employing inclined incidence of the light is an increased danger of contamination which makes itself noticeable in such form that holes which when viewed under the microscope appear completely clear cause upon inclined passage of the light a light dissipation of` more than 50% .owing to opaque scales which cover up a part of the inside.

Fig. 2 shows how this danger is overcome according to the invention. 'I'he holes are punched out, not of the disk II itself, but oi' thin sheets 22, preferably of copper foil, covering larger holes of the disk. 'I'he thickness of the sheets may be approximately equal to the diameter of the holes.

(Cl. P18-7.6)

The cross-section of the holes I2 is made, in order to obtain a circular or square cross-section ofthe light bundle, elliptic (Fig. 2c) resp. rectangular. (Fig. 2U). The proportion of width to length of these cross-sections had to be cos a, if the thickness of the sheets 22 were zero, and has to be still less as the thickness is relatively considerable. i

-Another method to obtain practically the same, result shows Fig. 3,v for example for a circular hole. 'I'he hole I2 is produced by a punch, which encloses together with the plane of the'disk the same angie u for which provision is made in respect ofr the subsequent ray of light.

'Ihe inclined punching of a precise hole in metal foil is, however, accompanied by the danger of the punch slipping, so that the hole gets Yinaccurate in its position. This disadvantage can only be overcome by very precise guiding of the. punch.

The two inventive ideas of Fig. 2 and Fig.` 3v may also be combined according to Fig. 4. In order to obtain a square bundle of light a rectangular hole,is punched obliquely at an angle a.

I claim:

1. In the television art a scanning disk which is traversed by the scanning light bundle at an oblique angle having scanning holes the projection of which onto a plane perpendicular to said` light bundle is a regular polygon. i.

2. In the television art a scanning disk which is traversed by the scanning light bundle at 'an obliquel angle having scanning holes the projection of which onto a plane perpendicular to said light bundle is a regular polygon, said holes beingpunched out of sheets of a thickness about equal to the diameter of the holes, said sheets covering larger holes in said disk.

3. In the" television art a scanning disk which y is traversed by the scanning light bundle at an oblique .angle having scanning holes the projection of which onto a plane perpendicular to said light bundle is a regular polygon and the walls of which are parallel to said light bundle.

KURT HEINZ GRAEFE. 

